A rare case of osteomalacia with an oronasal fistula developing after sequestrectomy is presented. The patient was a 45-year-old woman who was referred to our hospital because of an intractable ulcer at the midline of the hard palate. She had an edentulous maxilla and wore a poorly fitting complete maxillary denture. Oral examination showed ulceration with a sequestrum under the prosthesis. Removal of the sequestrum extending from the oral cavity to the nostrils resulted in an oronasal fistula of the hard palate. The case was finally diagnosed as osteomalacia based on the results of radiographic and serum chemical examinations. In this patient, continuous pressure caused by the poorly fitting maxillary denture induced the sequestrum in the hard palate, which was thin and fragile because of osteomalacia.
